Koko The Gorilla, The Ape Who Speaks Sign Language

Koko the gorilla is probably the best-spoken animal in the world. After all, she's had more than 40 years of practice. She began in 1972, when animal psychologist Francine Patterson taught her American Sign Language as a part of her PhD project to see if humans and gorillas could communicate.

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A Lifelong Friendship

Teaching Koko sign language eventually became a lifelong hobby and caregiving relationship to Dr. Patterson. In the early stages of teaching, Koko learned one new sign every month. But soon enough, Koko was combining signs to convey more complex concepts, pairing up signs for "more" and "eat," for example, to ask for more food.

The Difference Between Vocab And Language

Over the course of 43 years, Koko has picked up more than 1,000 words of modified American Sign Language, which is a vocabulary comparable to that of a 3-year-old child. But though she certainly has an impressive number of words in her stable (for a gorilla, anyway), some researchers question to what extent she truly uses language. As psychologist Herbert Terrace wrote to the New York Review of Books, the majority of Koko's signs are elicited, not spontaneous, and her ability to understand novel signs and spoken language "is not evidence of grammatical competence."